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<h2>SCROLL_CB</h2>
<p>Called when some manipulation is made to the scrollbar. The canvas is 
automatically redrawn only if this callback is NOT defined.</p>
<p>(GTK 2.8)</p>
<h3>Callback</h3>
<pre>int function(Ihandle *<strong>ih</strong>, int <strong>op</strong>, float <strong>posx</strong>, float <strong>posy</strong>); [in C]
<strong>elem</strong>:scroll_cb(<strong>op</strong>, <strong>posx</strong>, <strong>posy</strong>: number) -&gt; (<strong>ret</strong>: number) [in Lua]</pre>
<p><strong>ih</strong>:
  identifier of the element that activated the event.<br>
<strong>op</strong>:
  indicates the operation performed on the 
  scrollbar.</p>
<blockquote>
<p>If the manipulation was made on the vertical 
  scrollbar, it can have the following values:</p>
</blockquote>
<pre>IUP_SBUP - line up
IUP_SBDN - line down
IUP_SBPGUP - page up
IUP_SBPGDN - page down
IUP_SBPOSV - vertical positioning
IUP_SBDRAGV - vertical drag </pre>
<blockquote>
<p>If it was on the horizontal scrollbar, the 
  following values are valid:</p>
</blockquote>
<pre>IUP_SBLEFT - column left
IUP_SBRIGHT - column right
IUP_SBPGLEFT - page left
IUP_SBPGRIGHT - page right
IUP_SBPOSH - horizontal positioning
IUP_SBDRAGH - horizontal drag</pre>
<p><strong>posx</strong>, <strong>posy</strong>:
  the same as the <b>ACTION</b>
  canvas callback (corresponding to the values 
  of attributes  POSX and  POSY).</p>

<h3>Notes</h3>

<p>IUP_SBDRAGH and IUP_SBDRAGV are not supported in GTK.</p>

<h3>Affects</h3>
<p><a href="../elem/iupcanvas.html">IupCanvas</a>,
  <a href="../ctrl/iupglcanvas.html">IupGLCanvas</a>,
<a href="../attrib/iup_scrollbar.html">SCROLLBAR</a></p>

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